Calculate percentages of a binary variable BY another variable in R

Question

I want to summarise the percentage of people that have been treated BY region.

I have created a dummy dataset for this purpose:

id <- seq(1:1000)
         


        

Answer 1

For completeness, here's how you can do it using ddply() from plyr:

library(plyr)
ddply(d[!is.na(d$id),],.(region),summarize,
      N = length(region),
      prop=mean(treatment==1))
#   region   N prop
# 1      A 200  0.5
# 2      B 200  0.5
# 3      C 200  0.5
# 4      D 200  0.5
# 5      E 200  0.5

This assumes that you want to deal with the NA values in id by removing the observation.